1. Field of the Invention
The present invention relates to an electromagnetic clutch apparatus.
2. Related Art
Disclosed in JP-A-2000-234634 is an electromagnetic clutch apparatus of a background art applied to a torque transmitting coupling. According to the electromagnetic clutch apparatus, a pilot clutch is engaged by attracting an armature by forming a magnetic path in a circulating shape by an electromagnet. A main clutch is controlled to be engaged by the electromagnet by exerting a press force to the main clutch by engaging the pilot clutch.
The electromagnetic clutch apparatus is formed with a through hole in a circular arc shape at the pilot clutch for forming the magnetic path and includes a bridge portion for maintaining a shape in a diameter direction of the pilot clutch between the through holes.
However, by the through hole, the magnetic path in the circulating shape surrounding the through hole is shortcut and there is a loss in a magnetic force. Therefore, in order to increase an engaging force, the electromagnet or the pilot clutch is large-sized, and an energy loss is brought about by increasing a supply current.